The present invention relates to flame-retardant polymer compositions containing ethylene copolymers. More especially, these compositions do not contain halogenated derivatives and are capable of being processed by conventional techniques into articles having good fire resistance, such as, in particular, insulating sheathings for electrical cables.
Improvement of the fire resistance of compositions containing polymer materials is a constant objective of the manufacturers and processors of these materials, directed towards obtaining a significant reduction in the inflammability and capacity for flame propagation of these materials. The use of halogenated derivatives as flame-retardant agents is well known, but has the great drawback of leading, on combustion, to toxic and corrosive gases. The manufacturers and processors have hence turned their attention to the development of compositions containing oxides, hydroxides or inorganic salts of metals, such as hydrated alumina and magnesium hydroxide.
However, the addition of such inorganic fillers in a sufficient amount to obtain good fire resistance leads to materials having mediocre mechanical properties and/or presenting great difficulties of processing by conventional methods such as extrusion. Thus, the addition of large amounts of hydrated alumina to an ethylene/alkyl (meth)acrylate copolymer leads to a composition whose mechanical properties are greatly inferior to those of said copolymer.